1 tablespoon butter, melted $
Cooking spray
2 (6-ounce) packages fresh baby spinach $
1 1/4 cups (5 ounces) shredded reduced-fat sharp cheddar cheese $
3/4 cup (3 ounces) shredded Monterey Jack cheese $
1 1/3 cups all-purpose flour (about 5 3/4 ounces) $
1 1/2 cups fat-free milk $
1 cup egg substitute
1 teaspoon salt $
1 teaspoon baking powder $
2 teaspoons Dijon mustard $
1/4 teaspoon freshly ground black pepper
1/8 teaspoon ground nutmeg
1/8 teaspoon ground red pepper